Self contained is the best choice while students are still in primary grades. The teacher gets to know the whole child and observes which subjects their students are strong in and which they need help with. The teacher will already know if they struggle in reading, that science and social studies will be hard for them as well. The flexibility in self contained lends to a higher academic environment and increased learning pace. For example: In my typical day of teaching self contained, I can determine that it okay to pass on SS for the day if we need to extend the Science lesson. I can determine that Math is going so well, that we can take the quiz earlier than expected. I can add more centers if we have time, and increase reading. By departmentalizing, you have taken all options away. The teacher has to fit in reading and writing and Social Studies before the student goes on to the next class where their 2nd teacher of the day has to get in Math and Science. There are too many pro points to list here on being self contained in primary. On the flip side, the only pro to having your child switch classes in 2nd grade is that her/his teacher may be spectacular in their one subject versus being spectacular in all 5 subjects.